In the present assignee's U.S. patent application Ser. Nos. 11/601,199, 11/606,742, and 11/788,597, all of which are incorporated herein by reference, devices and methods are disclosed for natural orifice procedures. Specifically, devices and methods are disclosed in which a medical instrument is advanced through the mouth or anus of a patient to resolve maladies with organs such as the gall bladder and appendix, and to treat diverticulosis. As understood herein, such procedures can be facilitated by using a relatively large outer tube through which one or more instruments such as endoscopes, e.g., colonoscopes, may be advanced to facilitate the desired procedure. It is to such outer tubes that the present invention is directed.